Merge pull request #25042 from mshabunin:doc-upgrade

Documentation transition to fresh Doxygen #25042

* current Doxygen version is 1.10, but we will use 1.9.8 for now due to issue with snippets (https://github.com/doxygen/doxygen/pull/10584)
* Doxyfile adapted to new version
* MathJax updated to 3.x
* `@relates` instructions removed temporarily due to issue in Doxygen (to avoid warnings)
* refactored matx.hpp - extracted matx.inl.hpp
* opencv_contrib - https://github.com/opencv/opencv_contrib/pull/3638

modules/gapi/include/opencv2/gapi.hpp

@@ -10,7 +10,7 @@
 
 #include <memory>
 
-/** \defgroup gapi G-API framework
+/** \defgroup gapi_ref G-API framework
 @{
     @defgroup gapi_main_classes G-API Main Classes
     @defgroup gapi_data_objects G-API Data Types

modules/gapi/include/opencv2/gapi/gcommon.hpp

@@ -249,6 +249,8 @@ template<typename T> struct wrap_serialize
 } // namespace s11n
 } // namespace gapi
 
+/** @} gapi_compile_args */
+
 /**
  * @brief Ask G-API to dump compiled graph in Graphviz format under
  * the given file name.
@@ -261,7 +263,6 @@ struct graph_dump_path
 {
     std::string m_dump_path;
 };
-/** @} */
 
 /**
  * @brief Ask G-API to use threaded executor when cv::GComputation
@@ -276,7 +277,6 @@ struct GAPI_EXPORTS use_threaded_executor
 
     uint32_t num_threads;
 };
-/** @} */
 
 namespace detail
 {

modules/gapi/include/opencv2/gapi/gstreaming.hpp

@@ -388,7 +388,6 @@ protected:
     /// @private
     std::shared_ptr<Priv> m_priv;
 };
-/** @} */
 
 namespace gapi {
 
@@ -413,7 +412,6 @@ struct GAPI_EXPORTS_W_SIMPLE queue_capacity
     GAPI_PROP_RW
     size_t capacity;
 };
-/** @} */
 } // namespace streaming
 } // namespace gapi
 
@@ -425,6 +423,8 @@ template<> struct CompileArgTag<cv::gapi::streaming::queue_capacity>
 };
 }
 
+/** @} gapi_main_classes */
+
 }
 
 #endif // OPENCV_GAPI_GSTREAMING_COMPILED_HPP

modules/gapi/include/opencv2/gapi/infer/ov.hpp

@@ -690,7 +690,6 @@ namespace wip { namespace ov {
  * taking into account the i/o data transfer.
  */
 struct benchmark_mode { };
-/** @} */
 
 } // namespace ov
 } // namespace wip